U.S. patent application number 12/606510 was filed with the patent office on 2010-02-25 for method of controlling an overrun operation of a motor vehicle, a control device for implementing the method, and a corresponding motor vehicle.
This patent application is currently assigned to Bayerische Motoren Werke Aktiengesellschaft. Invention is credited to Joachim FROESCHL.
Application Number | 20100044130 12/606510 |
Document ID | / |
Family ID | 39717642 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100044130 |
Kind Code |
A1 |
FROESCHL; Joachim |
February 25, 2010 |
Method of Controlling an Overrun Operation of a Motor Vehicle, a
Control Device for Implementing the Method, and a Corresponding
Motor Vehicle
Abstract
A method controls an overrun operation in a motor vehicle,
wherein, in the presence of predetermined switch-off conditions, an
overrun switch-off of the internal-combustion engine takes place by
interrupting the fuel feed, and wherein, when a predetermined
restoring speed is reached or fallen below, the fuel feed is
resumed. Starting from an operating state with an activated overrun
switch-off, the transmission line between the output of the engine
and the input of the transmission device is monitored as to whether
a torque difference is occurring which is greater than or equal to
a predetermined limit torque. In such a case, the
internal-combustion engine is driven by an electric machine coupled
with the crankshaft of the internal-combustion engine such that a
rotational speed of the internal-combustion engine is adjusted to
be greater than or equal to the restoring speed.
Inventors: |
FROESCHL; Joachim;
(Herrsching, DE) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Bayerische Motoren Werke
Aktiengesellschaft
Muenchen
DE
|
Family ID: |
39717642 |
Appl. No.: |
12/606510 |
Filed: |
October 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EP2008/003977 |
May 16, 2008 |
|
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12606510 |
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Current U.S.
Class: |
180/65.25 ;
123/394; 180/54.1; 180/65.21; 60/706; 701/110; 701/51; 701/67 |
Current CPC
Class: |
B60W 10/02 20130101;
B60W 2510/0216 20130101; B60W 30/18072 20130101; Y02T 10/62
20130101; B60W 30/1884 20130101; B60W 10/06 20130101; B60W
2510/0661 20130101; B60W 10/08 20130101; Y02T 10/6234 20130101;
B60W 2540/16 20130101; B60W 2050/001 20130101; B60L 2240/486
20130101; B60K 6/442 20130101; B60W 2710/0644 20130101; B60W 20/00
20130101; B60K 6/20 20130101; B60W 2510/0233 20130101 |
Class at
Publication: |
180/65.25 ;
123/394; 701/110; 60/706; 180/54.1; 701/67; 701/51; 180/65.21 |
International
Class: |
B60K 6/48 20071001
B60K006/48; F02B 61/02 20060101 F02B061/02; G06F 19/00 20060101
G06F019/00; F01B 21/04 20060101 F01B021/04; F02D 41/00 20060101
F02D041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 2007 |
DE |
10 2007 026 354.8 |
Claims
1. A method of controlling an overrun operation in a motor vehicle
equipped with an internal combustion engine and an electric
machine, wherein an overrun switch-off of the internal combustion
engine occurs under predetermined switch-off conditions by
interrupting a fuel feed to the internal combustion engine, and
wherein upon reaching or falling below a predetermined restoring
speed, the fuel feed is resumed, the method comprising the acts of:
in an operating condition with the overrun switch-off active,
monitoring a transmission line between an output of the
internal-combustion engine and an input of a transmission device
for whether a torque difference occurs that is greater than or
equal to a predetermined limit torque; and when said torque
difference occurs, driving the internal combustion engine by the
electric machine that is coupled with a crankshaft of the internal
combustion engine to adjust a rotational speed of the internal
combustion engine to be greater than or equal to the restoring
speed.
2. The method according to claim 1, wherein the act of monitoring a
transmission line further comprises the acts of: monitoring a
separating clutch arranged between the internal combustion engine
and the transmission device; and in an event that the transmission
line is separated by way of the separating clutch by a
predetermined extent, determining that the torque difference
greater than or equal to the predetermined limit torque has been
reached.
3. The method according to claim 2, further comprising the acts of:
monitoring an operational duration of the separating clutch; and
when a predetermined maximum operational duration has been reached
or exceeded, resuming the fuel feed to the internal combustion
engine even if a torque difference greater than or equal to the
predetermined limit torque is present.
4. The method according to claim 1, wherein the monitoring act
further comprises the acts of: monitoring a converter device
arranged between the internal combustion engine and the
transmission device; and in an event that the transmission line is
separated by a predetermined extent by way of the converter device,
determining that the torque difference greater than or equal to the
predetermined limit value has been reached.
5. A control unit of a motor vehicle equipped with an internal
combustion engine and an electric machine, the control unit
comprising a computer readable medium having stored therein program
code segments that: in an operating condition with the overrun
switch-off active, control a monitoring of a transmission line
between an output of the internal-combustion engine and an input of
a transmission device for whether a torque difference occurs that
is greater than or equal to a predetermined limit torque; and when
said torque difference occurs, control a driving of the internal
combustion engine by the electric machine that is coupled with a
crankshaft of the internal combustion engine to adjust a rotational
speed of the internal combustion engine to be greater than or equal
to the restoring speed.
6. A motor vehicle, comprising: an internal combustion engine for
generating a drive torque that acts upon at least one drive wheel;
a transmission device coupleable with the internal combustion
engine by which different gear positions are adjustable; means for
at least temporarily separating a transmission line between an
output of the internal-combustion engine and an input of the
transmission device such that torques at the output of the internal
combustion engine and at the input of the transmission device
differ; an electric machine for generating a motor torque acting
upon a crankshaft of the internal combustion engine, the electric
machine being operatively configured such that, even in an event of
a complete separation of the transmission line, additional torque
can be generated via the electric machine for driving the internal
combustion engine; and a control unit operatively configured such
that, starting from an operating condition with an activated
overrun switch-off, the transmission line between the output of the
internal combustion engine and the input of the transmission device
is monitored as to whether a torque difference greater than or
equal to a predetermined limit torque is occurring and, in such a
case, the internal combustion engine is driven by way of the
electric machine coupled with the crankshaft so that a rotational
speed of the internal combustion engine is adjusted to be greater
than a restoring speed.
7. The motor vehicle according to claim 6, wherein presence of the
torque difference is determined as a function of an operating
condition of a separating clutch arranged between the
internal-combustion engine and the transmission device.
8. The motor vehicle according to claim 6, wherein presence of the
torque difference is determined as a function of an operating
condition of a converter device arranged between the
internal-combustion engine and the transmission device.
9. The motor vehicle according to claim 6, wherein the electric
machine is constructed as a crankshaft starter generator arranged
directly on a drive shaft connected with the crankshaft of the
internal-combustion engine for generating an additional drive
torque acting upon the at least one drive wheel.
10. The motor vehicle according to claim 7, wherein the electric
machine is constructed as a crankshaft starter generator arranged
directly on a drive shaft connected with the crankshaft of the
internal-combustion engine for generating an additional drive
torque acting upon the at least one drive wheel.
11. The motor vehicle according to claim 8, wherein the electric
machine is constructed as a crankshaft starter generator arranged
directly on a drive shaft connected with the crankshaft of the
internal-combustion engine for generating an additional drive
torque acting upon the at least one drive wheel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of PCT International
Application No. PCT/EP2008/003977, filed May 16, 2008, which claims
priority under 35 U.S.C. .sctn.119 to German Patent Application No.
DE 10 2007 026 354.8, filed Jun. 6, 2007, the entire disclosures of
which are herein expressly incorporated by reference.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] The invention relates to a method of controlling an overrun
condition of a motor vehicle, as well as a control device for
implementing the method, and a corresponding motor vehicle.
[0003] When an existing overrun condition is detected, conventional
controls for the overrun condition of a motor vehicle will
interrupt the fuel feed. When a predetermined restoring speed of
the deactivated or not fired (and Notionally coupled)
internal-combustion engine is reached or there is a falling below
this predetermined restoring speed, then the fuel feed is resumed
and the internal-combustion engine is activated or subsequently
fired.
[0004] For controlling an overrun condition in the case of a hybrid
vehicle, it is known from DE 10 2004 052 786 A1 to interrupt the
fuel feed when an overrun condition exists, and to activate the
fuel feed again when a predetermined restoring speed has been
reached or there is a falling below this predetermined restoring
speed. In this case, it is provided that the restoring speed is
defined to be as close as possible to just above the idling speed.
This is achieved in that, during hot running conditions of the
internal-combustion engine, the restoring speed is set to a value
of not more than 200 rpm above the idling speed of the
internal-combustion engine. Such a reduction of the restoring speed
can be carried out without having to expect impairment of the
operation of the internal-combustion engine because, in the event
of a declining idling speed, when the internal-combustion engine is
started again (restart), by way of the existing electric machine of
the hybrid drive, a drive torque can be generated which assists the
internal-combustion engine. This measure results in reduced fuel
consumption.
[0005] It is an object of the invention to provide a method, a
device for implementing the method, and a correspondingly
constructed motor vehicle respectively, whereby additional fuel can
be saved.
[0006] The invention is based on the recognition that, in the case
of conventional systems, the internal-combustion engine is
activated for brief periods of time during shifting operations,
particularly during backshifting operations when driving downhill,
in order to prevent a decrease of the crankshaft rotation as a
result of existing friction losses of the internal-combustion
engine (for example, when the transmission line is disengaged by
way of a clutch).
[0007] According to the invention, starting from an operating state
with activated overrun cut-off, i.e., when the internal-combustion
engine is deactivated or when the internal-combustion engine's
drive train is coupled while the fuel feed is deactivated, the
method monitors whether the torque at the output of the motion
coupled internal combustion engine has fallen or is reduced by at
least a predetermined amount or a predetermined order of magnitude
with respect to the torque at the transmission input. In the event
that this is so, an additional torque is generated according to the
invention by way of an electric machine coupled with the crankshaft
of the internal-combustion engine and is transmitted to the
crankshaft such that the internal-combustion engine does not reach
or fall below the predetermined restoring speed.
[0008] In a preferred embodiment of the invention, either a gear
shift signal indicating an imminent gear change, a clutch operating
signal indication an operation of the clutch, or a converter
activating signal indicating an operation of the converter device
(or in each case, a corresponding correlating signal) is detected
and analyzed for this purpose. Briefly stated, a signal is detected
and analyzed which indicates an imminent gear change or an at least
partial neutralization (caused particularly by an imminent gear
change) of the power or torque coupling of the transmission line
(drive train) between the internal-combustion engine output and the
input of the transmission unit (and therefore a corresponding
differential torque).
[0009] In a further development of the embodiment with a monitored
separating clutch (for example, in the case of manual
transmissions), it may be provided to monitor the operational
duration of the separating clutch and, when a predetermined maximum
operational duration is exceeded, to resume the fuel feed to the
internal-combustion engine even in the presence of a torque
difference greater than or equal to a predetermined differential or
limit torque. Analogous to the above-described method, the
invention also includes a control device, which is suitable for
implementing the described method or to correspondingly control the
internal-combustion engine and the electric machine, as well as to
a motor vehicle having a corresponding control device.
[0010] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of one or more preferred embodiments when considered in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIGS. 1 to 3 are graphical diagrams illustrating the
temporal course of the rotational speed of the internal-combustion
engine, the temporal course of the overrun switch-off signal and
the temporal course of a gear shift signal, when the overrun
condition is controlled according to the method of the invention;
and
[0012] FIG. 4 is a schematic representation of a drive unit for a
motor vehicle according to the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates the temporal course of the rotational
speed nBKM of an internal-combustion engine of a motor vehicle
controlled according to the method of the invention in the overrun
condition. Starting from an active overrun state, during which, in
the presence of predetermined overrun conditions, the fuel feed to
the internal-combustion engine 2 is interrupted or deactivated (and
the internal-combustion engine is motionally coupled only as a
result of a not separated drive train), a gear shift signal
S.sub.GW is detected at a point in time t.sub.0 at which the
rotational speed n.sub.BKM of the internal-combustion engine has a
value above a predetermined restoring speed n.sub.w.
[0014] As a result of the detected gear shift signal S.sub.GW, an
electric machine 4 coupled with the crankshaft of the
internal-combustion engine 2 is controlled such that, by way of the
electric machine 4 (preferably for the duration of the gear change
or during the time period in which the transmission line is at
least partially separated with respect to the torque between the
internal-combustion engine output and the transmission input), a
torque is generated. This torque acts upon the crankshaft of the
internal-combustion engine 2, whereby the internal-combustion
engine 2 (even when the transmission line is completely separated)
is held at a predetermined minimum rotational speed n.sub.min. It
is thereby achieved that, even in the case of a partially or
completely separated transmission line, the internal-combustion
engine 2 is held (motionally coupled) at a rotational speed
n.sub.min greater than or equal to the predetermined restoring
speed n.sub.w and an activating of the fuel feed and therefore an
activating of the internal-combustion engine 2 does not take place,
thus saving fuel.
[0015] FIG. 2 illustrates an overrun switch-off signal S.sub.SA, in
the case of which, at a level "one" or "high" signal level, the
overrun switch-off is activated (fuel feed deactivated), and a
"zero" or "low" signal level means an interruption or termination
of the overrun switch-off. In the illustrated graph, as a result of
the method according to the invention, the overrun switch-off is
not interrupted even in the case of a gear change or a detected
separation of the transmission line. The fuel consumption is
additionally reduced in this manner.
[0016] FIG. 3, in addition, illustrates the temporal course of the
gear shift signal S.sub.GW, which contains information as to
whether a gear change is imminent or a possibly existing separating
clutch 6 is operated, or the like. In this case, the signal
S.sub.GW may be active for the entire duration (between t.sub.1 and
t.sub.2) of the opened separating clutch 6 and may determine the
duration for which, as described above, the rotational speed of the
internal-combustion engine is adjusted to active (particularly
reset) by way of the electric machine 4. As a further development
of the invention, in an embodiment, in which the transmission line
is separated by way of a separating clutch 6 during a gear change,
the operational duration of the separating clutch 6 can be
monitored so that, when a predetermined maximum operational
duration T.sub.max is reached or exceeded, the fuel feed to the
internal-combustion engine is resumed (even in the presence of a
torque difference greater than or equal to the predetermined limit
torque or when the transmission line is separated by way of the
separating clutch).
[0017] In FIG. 4, an embodiment of a transmission line for a motor
vehicle according to the invention is illustrated. The transmission
line includes an internal-combustion engine 2 for generating a
drive torque acting upon drive wheels R. Furthermore, an electric
machine 4 coupled with the internal-combustion engine 2, a
separating clutch 6, as well as a transmission unit 8 are disposed
in the illustrated transmission line. The electric machine 4 is
preferably arranged on the drive shaft (constructed particularly as
a crankshaft starter generator whose rotor is arranged directly on
the drive shaft) coupled with the crankshaft of the
internal-combustion engine 2. As an alternative, the electric
machine 4 can also be arranged arbitrarily in a manner detached
from the drive shaft and can act upon the drive shaft (or the
crankshaft of the internal-combustion engine 2) by way of a belt
drive, chain drive, or the like.
[0018] In addition, an energy accumulating device 10 (such as a
battery and/or capacitor unit) is present, which is electrically
connected with the electric machine 4 by way of an electronic
coupling system 12 including an inverter unit. By way of this
electronic coupling system 12, on the one hand, the electric
machine 4 can be supplied with energy; on the other hand, in the
event that the electric machine 4 is operated as a generator (for
example, in the case of a recuperation operation), the energy
accumulating unit 10 can be supplied with charge current.
[0019] By way of a control unit 14, the drive unit or the overrun
operation of the internal-combustion engine 2 is controlled
according to the method of the invention. For example, by way of
the control unit 14 and a corresponding sensor system (not shown),
the operating condition of the separating clutch 6 is monitored for
this purpose. In the event that the separating clutch 6 is in an at
least partially opened condition (preferably, in a completely
opened/closed condition), the electric machine 4 is controlled such
that, by way of the latter, a motor torque is generated and is
transmitted to the crankshaft of the internal-combustion engine 2.
The electric machine 4 is controlled in such a manner that the
internal-combustion engine 2 rotates at an internal-combustion
engine (motionally coupled) rotational speed amounting to a
predetermined minimum rotational speed n.sub.min. The predetermined
minimum rotational speed n.sub.min is greater than or equal to the
predetermined restoring speed n.sub.w.
[0020] In the illustrated embodiment, the control unit 14 is
constructed as a control unit which, in addition to the described
functionality of the overrun switch-off, particularly includes
timing gear functions. The described functionality is preferably
integrated in a conventional timing gear.
[0021] The invention is not limited to the illustrated embodiment
with a separating clutch 6 arranged in the transmission line. On
the contrary, other embodiments with an automatic transmission and
a converter device are contemplated. In a particularly preferred
embodiment, the electric machine 4, in addition to the energy
accumulating device 10 and the coupling unit 12, is constructed
such that it can act as a sole or as an additional driving device
of the transmission line. For this embodiment, an additional
separating clutch TK is arranged between the internal-combustion
engine 2 and the electric machine 4, which would also be
controllable by way of the control unit 14.
[0022] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *